The kiss: Olivia Arthur’s series captured an unseen women’s world of late-night partying and alcohol in Jeddah, 2010.
Photograph: Olivia Arthur/Magnum Photos

In 1960, the Magnum photographer Eve Arnold spent a year following Malcolm X and the Nation of Islam movement around the United States. The white, female photographer and the leader of black America’s radical movement found they both understood the power of images. Malcolm X helped Arnold, though his followers were not always happy to see her and after one rally she found the back of her jersey riddled with holes – left by the cigarettes people had been jabbing into her back. The result of Arnold’s work was a series of pictures that included an iconic image – with the sharp and handsome Malcolm X sitting in profile, his hat tilted forward and a ring on his finger bearing the star and crescent moon.

Arnold was a talented photographer from a legendary agency. Magnum was set up 70 years ago this year by a small group of photojournalists led by Henri Cartier-Bresson, Robert Capa, George Rodger and Chim Seymour. The agency was not just a leader in providing the definitive – and often first – images of mid-20th century history, it also recognised that women belonged to what Cartier-Bresson called its “community of thought”. By 1957, two of its 15 owner-members were women – including Arnold and Inge Morath. Some of their pictures still lurk in our collective subconsciousness as categorical representations of certain people, places or moments in history. It would take the New York Times, by comparison, two more decades to hire its first female photographer.

For several decades, women were a small but core part of Magnum’s operation. Marilyn Silverstone, Susan Meiselas, Mary Ellen Mark and Martine Franck also joined. But between 1983 and 2009, only one – Lise Sarfati – was admitted as a full member, and she later resigned. It is only in the last dozen years that Magnum – where “nominee” members take four or more years to make it full membership – has begun to redress the imbalance.

Arnold and Morath joined during the 1950s around the time early members, such as Capa, Seymour and Werner Bischof died. All had followed Capa’s rule that “if your pictures aren’t good enough, you’re not close enough” and were killed, respectively, after stepping on a landmine in Indochina, being machine-gunned in Suez and driving off an Andean mountain road. Their deaths were a sign of the dedication Magnum expected of its members – who considered themselves a hybrid of photojournalist and artist. They still do. That makes the agency notoriously anarchic. Magnum’s biographer Russell Miller describes meetings marked by tantrums and slammed doors. “Magnum isn’t a democracy, it’s anarchy,” he says. A former employee was even more candid. “It’s like the inmates taking over the asylum,” he said. “It’s mob rule.”

Morath was a Magnum editor before starting to take her own photos in 1951. She became, among other things, a photographer of Hollywood stars and even saved the life of the Second World War hero, the actor Audie Murphy, after he injured himself during one of director John Huston’s duck shoots. Morath pulled his boat back to shore by swimming in front of it and using her bra strap as a tow rope. In one of her best-known images, an off-guard Marilyn Monroe raises her eyes to Morath’s camera, warmth shining through the glamour during a break in the filming of The Misfits.

Both Morath and Arnold befriended Monroe, and their photographs of her reveal their ability to build intimacy and trust. “She doted on the pictures Inge Morath had taken of her, sensing real affection,” Monroe’s then husband, playwright Arthur Miller, later recalled. “Marilyn liked her at once, appreciating her considerate kindness and the absence – remarkable in a photographer – of aggression.” Morath went on to marry Miller after he separated from Monroe. Their daughter, Rebecca Miller, is the film director and partner of Daniel Day-Lewis.

Much has changed since the glory days. Internet and digital phone cameras are bringing more radical change but, as a new generation of women builds a presence at Magnum, some things remain the same. “People often don’t see beyond you as a person with a camera; they don’t think of you as a professional and they let their guard down,” says Olivia Arthur, an Oxford mathematics graduate who was an early recruit to the new wave of Magnum women.

Arthur’s Jeddah Diary series, an intimate portrait of young women in Saudi Arabia, is a prime example of this unsought advantage. Her pictures speak of secret partying, alcohol, lesbians and hook-ups. “It’s an extreme example. But I had so much access to a world that couldn’t even have been seen by a man,” she explains. Arthur provides not just photographs but also text. She finds a festive atmosphere among women in a theme park, for example, where the only photograph she can publish is of an empty fairground ride. “The lesbian crowd is at the bowling alley, hanging out, flirting, kissing,” Arthur writes. “Walking around with a girl dressed like a man, security approaches. ‘I’m getting complaints,’ she says. ‘Women are afraid, they think there is a man here… Can’t you be more feminine?’” Some of Arthur’s pictures were tantalisingly held below a bright light and photographed again to hide the subject’s face. “I had access to something that couldn’t all be shared.”

“The industry is very male dominated, but when you make your work, personally I think it’s easier to be a woman,” says Susan Meiselas, who joined in 1976 and links the generation of Arnold and Morath with the newcomers. Her entry into Magnum was an example of just how willing members are to take apparently risky bets on new talent, despite the famously rigorous selection process which now sees aspirants present three different portfolios over four years. Meiselas had made her name taking pictures of itinerant strippers in New England fairgrounds. These hung on the walls of the Whitney Museum in New York, but she had little experience of photojournalism. When in 1978 she set out for Nicaragua – a country in open rebellion against strongman Anastasio Somoza – she did not even know how many rolls of replacement film she could request (she asked for 10 and Magnum sent 100). Her enthusiasm was such that experienced hands soon warned she was taking the “get close” philosophy too literally. She turned into a much-praised conflict photographer. Her “Molotov Man” picture of a beret-clad Sandinista fighter with Mick Jagger looks captured both the bravado and, for some, the romance of battling US-backed regimes in central America during the 1980s.

There has always been a tension at Magnum between art and reportage. Even stronger has been the tension between art and money. For years the agency struggled to make a decent profit. In 2010 Magnum sold much of its New York archive of press prints to billionaire Michael Dell – who then gifted them to the University of Texas – with an insurance value reported at more than $100m. The market is now pushing photographers towards the art side of the balance. Photographers like Arnold were given months to carry out magazine commissions, while today’s Magnum members are more likely to be given days. As a result much of the agency’s best photography is to be found in limited-edition books.

For some, this is a return to their roots. Cristina García Rodero, a Spanish member, had been taking photographs for decades before joining in 2005. Her first project had been an epic journey taking pictures of Spanish fiestas which took 15 years to complete – and became a book. When we meet in Madrid she has just returned from India, and is considering setting out for Brazil to photograph Easter rituals. Her festival obsession means she now also travels to the Nevada desert for Burning Man, to Berlin’s Love Parade and to other erotic festivals. “I guess I probably look at those in a different way to a male photographer,” she says.

The degree of ambition – and amount of work - required to be a Magnum photographer has been one of the blocks to women. Men do not always have the same impediments. “I remember war photographers who were back in the field a few days after a child had been born,” said Meiselas, who recalls at least one talented female nominee leaving Magnum because it did not fit with her family life. Arthur, who I catch in jet-lagged mode in London between trips to India and New York, shares her life – and small daughter – with a fellow photographer. “He’s very supportive, and we are able to juggle,” she says.

A simple smile: Marilyn Monroe during a break in filming The Misfits, New York, 1960. Later Arthur Miller revealed how much she liked the Inge Morath shot. Photograph: The Inge Morath Foundation/Magnum Photos

Magnum photographers have, in terms of nationality, always been a diverse group. So what happened to women during that 26-year lull? Meiselas believes that, in part, the agency’s history of incorporating women mirrors that of society and feminism – with women photographers joining during the militant 70s and the bold early 21st century, but not during the low days of the late 20th century. Three of the nine photographers now going through the process of acquiring membership are women – and Magnum’s foundation gives an annual Inge Morath Award to young female photographers wanting to complete a long-term project. One of the current Magnum nominees, Newsha Tavakolian, is the subject of a picture by another of the agency’s photographers, her fellow Iranian Abbas. It shows her at work in a press pack among a bunch of short-sleeved, bare-headed cameramen. Tavakolian is the only one obliged to cover her head and arms. It is a reminder that in some places women struggle just to become professional photographers, making the idea of joining Magnum an almost impossible dream.